The current method we using (0.3g of plant + 0.5mL H2O2 + 2mL HNO3) for plant digestion has low Fe recoveries probably due to the precipitation of Fe out of solution. I would like know how can I improve Fe recoveries?
Kindly mention if the 0.3g is fresh weight or dried weight. Moreover, Kindly also mention the temperature and time for digestion of the sample and which method you used to measure Fe. Normally the sample is digested completely to recover all the metals such as at 220 to 240 degree c for 30 minutes in specialized containers and equipment. At this stage sample should not be visible. Then you filter it and use for measurement.
Its 0.3 g of dried weight. The pre-digestion is 16 hrs while the digestion is 2 hrs at 120oC. The concentration of Fe was measured on the ICP.
If it was digested completely then there should not be any problem of recovery. If it is not digested completely then you may digest it again. Are you using ICP AES or OES or ICP MS.
Hi Khuram,
Its ICP-OES.
We do get some precipitates but we expect them to be composed of silica. For instance when we have low concentration of Fe we get good recoveries even there's precipitates.
Higher concentration of Silica is a problem for digestion. I could not see any other reason. If sample is digested properly then metals would be soluble due to acidic environment.
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